The long-range purpose of the project is to study the biochemistry, morphology, pharmacology and physiology of inner ear neurons and other cells and to describe the mechanisms of their interactions. 1. Immunocytochemical evidence indicates that at least two opioid peptides are present in the guinea pig cochlea. One of these is met-enkephalin, as indicated by biochemical studies using high performance liquid chromatography (HPLC) and radio immuno assay (RIA). 2. Complementing immunocytochemical studies have demonstrated the presence of enkephalin-like immunoreactivity in cells and nerve fibers in the guinea pig retina. 3. The study of the differential distribution of aspartate aminotransferase and glutaminase-like immunoreactivity at a high level in spiral ganglion cells in the modiolus and in nerve fibers and endings in the organ of Corti in ongoing. 4. An immunocytochemical study of the distribution of choline acetyltransferase in the cochlea has been initiated.